1. Field of Invention
This invention relates to substituted polybenzimidazole products. More particularly, the invention relates to polybenzimidazole esters and carboxylic acids and a process for their production.
2. Prior Art
Polybenzimidazoles are a well known class of polymers characterized by a high degree of thermal and chemical stability. As a result, polybenzimidazole polymers have found application in a wide variety of uses such as membranes, ultrafilters, reverse osmosis devices and other separatory media.
While polybenzimidazole polymers are generally more resistant to chemical attack than are other types of polymers, such as cellulose acetate polymers, reaction at the nitrogen/hydrogen bond on the imidazole ring under certain conditions will occur, thereby adversely affecting the performance of the polymer. One means of avoiding this reaction is to chemically modify the polybenzimidazole polymer, for example, by crosslinking the polymer as disclosed in U.S. Pat. Nos. 4,020,142 and 4,154,919.
Another method of reducing the reactivity of the polybenzimidazole polymer is by replacing the imidazole hydrogen with a less reactive substituent. Several patents have disclosed substituted polybenzimidazole polymers. For example, U.S. Pat. No. 4,377,546 discloses a substituted polybenzimidazole wherein the hydrogen on the imidazole ring is replaced by a phenyl group.
U.S. Pat. No. 4,579,915 discloses a substituted polybenzimidazole polymer wherein the imidazole hydrogen has been replaced by the following substituent: ##STR1## wherein R is nitro, cyano or trifluoromethyl, and R' is hydrogen, alkyl, nitro, cyano or trifluoromethyl.
U.S. Pat. No. 3,943,125 discloses a vast array of substituted polybenzimidazole polymers produced by (1) reacting substituted tetraamino pyridines, or their acid salts with a substantially molar quantity of a suitable acid halide or dianhydride to produce substituted precyclized intermediates and (2) cyclodehydrating and crosslinking these intermediates to produce the substituted polybenzimidazole polymers. However, this patent fails to disclose polybenzimidazole carboxylic acids or esters for a process for their production.
U.S. Pat. No. 3,518,234 discloses a process for the preparation of aryl substituted polybenzimidazole polymers by the cyclo-dehydration of aromatic polyamide imines, but again fails to disclose polybenzimidazole carboxylic acids or esters or a process for their production.
An hydroxyl-modified polybenzimidazole polymer prepared by reacting a polybenzimidazole polymer with an omega-halo-alkanol or a 1,2-alkylene oxide is disclosed in U.S. Pat. No. 3,578,644. A separate process for preparing hydroxyl-modified polybenzimidazole polymers is disclosed in U.S. Pat. No. 4,549,388.
Although various substituted polybenzimidazol polymers have been disclosed in the prior art, none disclose carboxylic acid or ester substituted polybenzimidazole polymers or a process for their production.
It is therefore an object of this invention to prepare novel polybenzimidazole esters.
A further object of this invention is to prepare novel polybenzimidazole carboxylic acids.
It is an additional object of this invention to disclose a process for the production of polybenzimidazole carboxylic acids and esters.
It is a still further object of this invention to disclose a process for the production of substituted polybenzimidazole articles which may be useful as separatory media.
These and other objects, as well as the scope, nature and utilization of this invention will be apparent to those skilled in the art from the following detailed description and appended claims.